JPS6373719A - Bipolar code identification circuit - Google Patents

Abstract

PURPOSE:To identify a code without any error even in a bipolar signal with unsharpened waveform by controlling a reference voltage to a small value when a duty signal corresponding to a pulse width is small and controlling the reference value to a large value when the duty signal is large. CONSTITUTION:When outputs 12, 13 of a transformer 1 are inputted to a couple of line receivers 2, 3, they are compared with a reference voltage V0 of a reference voltage control circuit 8 and both the positive and negative bipolar signals are detected respectively. A duty detection circuit 7 outputs a voltage proportional to the pulse width of the output pulse of line receivers 2, 3, and the reference voltage control circuit 8 increases the identification level (reference voltage)V0 of the line receivers 2, 3 when the output voltage of the circuit 7 is large and decreases the identification level V0 when the output voltage of the duty detection circuit 7 is small. Thus, the operation is balanced and made stable when the duty signal reaches a value (e.g., 50%).

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a bipolar code identification circuit that identifies the code of a bipolar signal that is band-limited in a transmission path and suffers from level fluctuations and waveform degradation.

(Prior Art) Conventionally, as shown in FIG. 3, this bipolar code identification circuit 1 applies a predetermined reference voltage V to the line receivers 2 and 3, and input signals 12 and 13 from the transformer 1 apply to this reference voltage. If the voltage is 70 or above, “1”, ■, if it is below, “0”
I identified it as Transformer 1 has input capabybora signal 1
This is for inverting the positive and negative polarities of the incoming polarity signal 11, so that the line receiver 2 identifies the positive polarity of the input polarity signal 11, and the line receiver 3 identifies the negative polarity of the input polarity signal 11.
1 is a clock extraction circuit, and 4 and 5 are D-flip-flops that output the same data 16.17 as input data 14 and 15 at the rising edge of the clock.

(Problems that the invention attempts to resolve) In the conventional example described above, the code identification level V0 is fixed, so it is not effective for identifying rectangular input Kabaibora numbers as shown in FIG. 2(a). However, as shown in Figure 2(b), for bipolar signals whose waveforms are blunted and the level has decreased due to band limitations due to the transmission path, it is difficult to distinguish between "1" and "O" of the incoming bipolar signals. The disadvantage was that it became impossible.

The present invention was developed in view of the above problems, and an object of the present invention is to provide a bipolar code identification circuit that can reliably identify bipolar signals that have undergone level reduction or waveform deterioration in a transmission path.

(Means for Solving the Problems) In order to solve the above-mentioned problems and achieve the above objects, the present invention provides a reference voltage control circuit that outputs a reference voltage, a reference voltage control circuit that outputs a reference voltage, and a bipolar signal between the reference voltage and the bipolar signal. a pair of line receivers that separately detect the positive polarity and non-polarity of the line receiver, and a pulse output means that synchronously outputs a positive polarity pulse and a negative polarity pulse based on the pulse outputs of the pair of line receivers; and a duty detection circuit that detects the pulse width of the pulse output and outputs a duty signal corresponding to the pulse width, and when the duty No. 3 is small, the reference voltage is set low and when the duty signal is large, the reference voltage is set. It is characterized by great control.

(Example) FIG. 1 is a block diagram showing one embodiment of the present invention.

1 is a transformer that inverts the polarity of the bipolar input signal 11. When the outputs 12 and 13 of the transformer 1 are input to a pair of line receivers 2 and 3, they are compared with the reference voltage ■ of the reference voltage control circuit 8 and the bipolar signal is The positive and negative polarities of are detected separately. 6 is a clock extraction circuit;
4 and 5 are D-flip-flops which operate at the rising edge of the clock of the clock extraction circuit 6 and output pulses corresponding to the pair of line receivers 2 and 3, that is, a positive pulse 16 and a negative pulse 17, respectively. 7 is a duty detection circuit which outputs a voltage (duty signal) proportional to the pulse width of the output pulse of the line receiver 2.3. Reference numeral 8 denotes a reference voltage control circuit, which functions to raise the discrimination level (reference voltage) v6 of the line receiver 2.3 when the output voltage of the duty detection circuit 7 becomes large, and when the output voltage of the duty detection circuit 7 becomes small. It functions to lower the discrimination level V.

When a bipolar signal as shown in FIG. 2(b) is input to the circuit configured in this way, the output voltage (duty signal) of the duty detection circuit 7 becomes small, so the reference voltage control circuit 8 It operates to lower the identification voltage (reference voltage V) of .3, and when the duty signal reaches a certain value (for example, 50%), the operation becomes balanced and stable. .

Furthermore, when the bipolar signal as shown in FIG. ), and in this case as well, the operation becomes balanced and stable when the duty reaches the above-mentioned predetermined value.

When the rectangular bipolar signal shown in FIG. 2(a) is inputted, the duty is already 50%, so the output voltage of the reference voltage control circuit 8 is ■. is kept constant.

(Effects of the Invention) As explained above, according to the present invention, it is possible to always set the optimum code discrimination level (reference voltage), so even bipolar signals whose waveforms are distorted due to band limitations on the transmission path can be set. This has the effect of allowing codes to be identified without error.

It is also effective in identifying bipolar signals whose S/N (signal-to-noise ratio) has deteriorated on a transmission path.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the bipolar code identification circuit of the present invention, FIG. 2 is a waveform diagram of a signal input to the bipolar code identification circuit, and FIG. 3 is a block diagram showing a conventional example. . 1...Transformer, 2,3...Line receiver, 4゜5...D-flip-flop, 6...Clock extraction circuit, 7...Duty detection circuit, 8...Base voltage control circuit.

Claims (1)

[Claims] A reference voltage control circuit that outputs a reference voltage, a pair of line receivers that compare the reference voltage and the signal voltage of the bipolar signal and separately detect the positive polarity and negative polarity of the bipolar signal, and the pair of line receivers. a pulse output means that synchronously outputs a positive polarity pulse and a negative polarity pulse based on the pulse output of the receiver; and a duty detection circuit that detects a pulse width of the pulse output and outputs a duty signal corresponding to the pulse width. 1. A bipolar code identification circuit, wherein the reference voltage is controlled to be small when the duty signal is small, and the reference voltage is controlled to be large when the duty signal is large.